MR. DOC-TOBER: The clueless look Alex Rodriguez wore after this strikeout was a common sight during the Yankees’ playoff run, before doctors discovered the left hip condition that ruined the struggling slugger’s swing. Photo: Anthony J. Causi

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The doctor scheduled to perform the upcoming hip surgery on Alex Rodriguez declared the injury had zero to do with steroids, but everything to do with A-Rod’s impotent October.

In an exclusive interview with The Post, Dr. Bryan Kelly described a patient whose left hip muscles had “just shut down,” becoming so weak that A-Rod had trouble doing a simple leg raise during exams. And, after seeing medical imaging of the hip, Kelly stated he had “no doubt” Rodriguez’s humiliating playoff meltdown was caused by the injury.

“I was more surprised that he was able to play at all with a hip that looked like that,” Kelly said. “Most people would not be able to play with a hip function like this and the imaging that looked like his.”

Rodriguez was diagnosed with a torn labrum and underlying impingement in the hip in November, but the surgery will still not be performed for two to four more weeks. Kelly and his rehab partner, Pete Draovitch, want all the inflammation out of the joint and to rebuild strength in the surrounding muscles because doing so will, in Kelly’s opinion, greatly speed up the post-operative rehab.

Kelly, the co-director of the Center for Hip Pain and Preservation at the Hospital for Special Surgery, believes Rodriguez will return shortly after the All-Star break — roughly six months following the surgery — and perform at a level commensurate to his past production. However, he has concerns based on: 1) not truly knowing the full extent of damage to the joint until the surgery, 2) not knowing how surgery and rehab on the left hip will impact an already surgically repaired right hip and 3) A-Rod’s age (37).

“He is fully intending on getting back,” Kelly said. “He does not want to leave baseball like he did at the end of the season.”

Here are Kelly’s views on the major issues surrounding Rodriguez’s injury:

DID THE INJURY CAUSE A-ROD’S WOEFUL POSTSEASON?

Rodriguez hit .116 (5-for-43) with no extra-base hits and 18 strikeouts in the playoffs, leading to his being pinch-hit for and eventually benched.

Kelly explained that 25 degrees of internal rotation is needed in the hips to produce an ideal swing and less than 10 percent leaves an athlete vulnerable. Kelly said Rodriguez probably was operating at well under 25 percent even in his best years as the hip impingement methodically did damage to the joint and labrum.

As a unique athlete, A-Rod compensated by using other muscles and having a strong pain tolerance. But by October, Kelly said, A-Rod “had zero degrees of motion through his hip.” That left Rodriguez trying to generate bat speed by altering his mechanics — opening his front left foot and mainly using his arms — and “he was not able to play at the level he needed to, directly as a result of the injury he has. I looked at the pictures, and there is no doubt the injury was what caused the reduction of performance.”

Kelly added,“I don’t see how it would be possible [for a player to have Rodriguez’s injury and be successful hitting]. The problems go back to Alex being such a good athlete. He can maybe hide some deficiencies, but at some point you can’t. Maybe he can work with 10 degrees of rotation for a while and hit reasonably well. At some point, though, the engine just broke down. You can’t generate power or speed. If you imagine a pitch coming in at 90 miles per hour, it would be a mechanical impossibility to do what you need to do based on [Rodriguez’s] hip function [in October].”

WAS THE INJURY RELATED TO STEROIDS?

Rodriguez admitted taking steroids while with the Rangers (2001-03), and suspicion persists the breakdown in now both hips was caused by the use. But Kelly said, “The easiest question anyone can ask is if this is related to steroid use. I can say with 100 percent certainty this is not a steroid injury at all. This is a mechanical injury, and mechanics are something you are born with.”

Kelly explained that by age 15 the hip has reached its mature shape and A-Rod’s impingement injury comes from two factors: a hereditary component (having a femoral head that is more egg-shaped than spherical and thus more likely to produce a labrum tear) and a developmental component (the external forces that come from repetitive motion in playing a high-level sport for a long period).

“Given Alex’s anatomy and sport, at some point in his career, the effects of the impingement would appear,” Kelly said.

WHY WAS THE INJURY NOT DIAGNOSED QUICKER?

Rodriguez underwent an MRI exam during the Division Series, but of his surgically repaired right hip. Kelly said understanding of hip injuries is still in its relative infancy — similar to where ACL knowledge was in the late-1970s — and because these injuries are “insidious,” coming over long periods of wear and tear without a traumatic separation or break, they are often easily undiagnosed or misdiagnosed.

In A-Rod’s case, Rodriguez was describing a lack of explosiveness rather than pain. The discomfort in other body parts came because he was putting a greater strain on those to compensate for the weakened left hip.

“I have done over 3,000 surgeries,” Kelly said, “and I have seen some [X-rays] where I say, ‘I’m not certain why [the patient] is having so much pain.’ I see others and say, ‘How were you able to play at all with a hip like this?’ His was more at that end of the spectrum.”

WHY IS THE SURGERY TAKING SO LONG TO PERFORM?

Draovitch, the head of hip rehabilitation at the Hospital for Special Surgery, has been working with A-Rod in Florida and New York while consulting with the Yankees medical staff. The initial read was that Rodriguez was “very, very weak” in the hip area, Kelly said, and patience in building up strength and reducing swelling on the front end will — in Kelly’s experience — save as much as six months of recovery time on the back end.

“I spend time slowing athletes down,” Kelly said. “It is a process. You can’t change the biological healing process. He is a very mature, incredibly dedicated athlete at this point. His maturity level allows him to recognize that you have to exercise patience to end up with the optimal outcome.”

WHAT CAN BE EXPECTED TO RESULT FROM THE SURGERY?

Kelly, who also serves as an associate team physician for the New York Giants, says he advises some athletes not to undergo the surgery because the damage seen through three-dimensional CT scan imaging and other tests is too extensive.

“Alex is not one of those patients,” Kelly said. “I truly believe we can make him significantly better, if not — ideally — back to the way he was before symptoms, or else I would not offer surgery.”

In the approximately two-hour surgery, Kelly will repair the torn labrum and then reshape the femoral head to make it round (from egg-shaped) to stop the bone from hitting the labrum during activities like swinging a bat. Only during the procedure will Kelly see the full extent of cartilage damage.

Plus, it is unclear how much damage the surgically repaired right hip may have incurred in compensating for the deteriorating left hip the past few years. Thus, A-Rod will have to go much slower in rehab this time than he did in 2009 because of a plan to not overload the right hip while rehabbing the left one.

“There is a threshold that makes full recovery more and more of a challenge and, at some point, it makes a return impossible,” Kelly said. “But we have looked at [Rodriguez’s] imaging, and we are all extremely optimistic he will get back.”

After a one-night hospital stay, the plan will be to get Rodriguez into progressive rehab immediately with the goal of a July return to the Yankees.

“I wouldn’t in any way say Alex is an easy case,” Kelly said. “There are a lot of complexities with him. … I would say we are extremely optimistic that we can get Alex back to performing at a high level, but he has a lot of obstacles in the way to get there.”